Development of ceramic composites for industrial wood-cutting tools

Industrial wood cutting is a highly demanding application for cutting tool materials as a wedge angle of similar to 50 degrees, a tip radius in the 1 mu m range, and high wear, temperature and corrosion resistance are needed. For this application Si3N4 based ceramic matrix composites (CMC) were developed. Cutting tests showed that reinforcing Si3N4 with 30 wt.% SiC gives a good balance between fracture toughness and wear resistance. The use of an yttria / lanthana sintering aid system resulted in a fine-grained microstructure without degrading the fracture toughness. Post heat treatment was essential for the integrity of the cutting edge. Finally, cutting tests proved that the CMC cutting tips had a 3-fold lifetime compared to tungsten carbide.